1. Field of the Invention
The present invention relates to a Stirling cycle engine, and more particularly to a Stirling cycle engine having radiation heating means.
2. Description of the Prior Art
Conventional Stirling cycle engines are operated under the Stirling cycle where the working gas is subjected to repeated working cycles each including an isovolumetric heating, an isothermal expansion, an isovolumetric cooling and an isothermal compression. For the isothermal expansion, the engine is provided with an external heat source. During the operating cycle, the energy of the working gas is taken out through a piston mechanism. FIG. 6 shows a typical example of a Stirling engine having radiation heating means for heating the cylinder heat of the engine.
Referring to FIG. 6, the engine has a cylinder 13 which is provided at a lower end portion with a crankcase 13a. At the upper end portion of the cylinder 13, there is provided a cylinder head 16. As shown in FIG. 6, the cylinder head 16 has a cylindrical skirt portion 16a which encircles the upper portion of the cylinder 13 to provide an annular space 16b between the upper portion of the cylinder 13 and the skirt 16a. The lower portion of the skirt 16a of the cylinder head 16 is radially expanded to provide an enlarged annular space 16c between the skirt 16a and the upper portion of the cylinder 13.
A displacer piston 10 is disposed in the upper portion of the cylinder 13 for axial sliding movements. The displacer piston 10 defines a chamber 6 of a variable volume between the piston and the cylinder head 16. The volume of the chamber 6 changes as the piston reciprocates in the cylinder 13. A piston rod 10a is secured at the upper end to the piston 10 and has a york 10b at the lower end. The lower end of the piston rod 10a is connected through the york 10b with a connecting rod 10c which connects the piston rod 10a with a crankshaft 12. The crankshaft 12 has an L-shaped crankarm having arm portions 12a and 12b. The connecting rod 10c is connected with the crankarm 12a. A working piston 11 is slidably mounted on the piston rod 10a and has an outer peripheral surface which slides along the inner wall of the cylinder 13. The working piston 11 is connected through a connecting rod 11a with the arm portion 12b of the crankshaft 12. In the cylinder 13, there is defined a second chamber 6 a between the displacer piston 10 and the working piston 11. The cylinder 13 is formed with a plurality of apertures 13a which connect the second chamber 6a with the enlarged annular chamber 16c. In the annular chamber 16b, there is provided a heat-accumulator 14. In the enlarged annular chamber 16c, there is a cooling unit 15.
The engine shown in FIG. 6 is applied in operation with heat radiation from an external source at the cylinder head 16 as shown by arrows 4. The displacer piston 10 and the working piston 11 are reciprocated in the cylinder 13 in an out-of-phase relationship. The phases of operations of the pistons 10 and 11 are determined by the angular relationship between the arm portions 12a and 12b of the crankshaft 12 so that the isovolumetric strokes and the expansion and compression strokes are applied to the working gas in the chambers 6, 16b, 16c and 6a. The cylinder head 16 receives thermal energy from the heat radiation applied thereto and gives the heat to the working gas in the chamber 6.
As the displacer piston 10 moves upward, the working gas in the chamber 6 is displaced to the annular chamber 16b and through the enlarged annular chamber 16c and the apertures 13a into the chamber 6a. As the working gas passes through the heat accumulator 14, the thermal energy in the gas is absorbed by the heat accumulator 14 to be stored therein. The working gas is then cooled by the cooling unit 15 in the enlarged annular chamber 15. In this period of operation, the movement of the working piston 11 is such that the overall volume of the chambers are substantially unchanged so that the working gas is subjected to the isovolumetric cooling.
Then, the working piston 11 is moved upward to compress the working gas in the chamber 6a. Thus, the isothermal compression is carried out. As the displacer piston 10 starts to move downward, the working gas in the chamber 6a is displaced from the chamber 6a through the annular chambers 16b and 16c into the chamber 6. During this period, the gas is heated by the heat accumulator 14 in the annular chamber 16b. The movement of the working piston 11 is such that the overall volume of the chamber is unchanged so that isovolumemetric heating is carried out. Thereafter, the working piston 11 is moved downward together with the displacer piston 10 so that the overall volume of the chambers is increased to thereby carry out the isothermal expansion. As the result of this operation, the crankshaft 12 is rotated in the direction shown by an arrow 23.
It will be noted in the conventional structure that the heat radiation is applied to the cylinder head to heat the same. The conventional engine is therefore of a heavy structure and has a slow responsive characteristics.